Control method of laundry machine

ABSTRACT

A control method of a laundry machine is disclosed. The control method of a laundry machine comprising a circulating step configured to circulate water inside the tub to re-supply the water to the tub, the circulating step implemented in a heating step.

TECHNICAL FIELD

The present invention relates to a control method of a laundry machine.

BACKGROUND ART

In general, a laundry machine may include washing, rinsing and spinning cycles. However, the conventional laundry machine has problems.

DISCLOSURE OF INVENTION Technical Problem

Accordingly, the present invention is directed to a control method of a laundry machine.

Solution to Problem

To solve the problems, an object of the present invention is to provide a control method comprising a circulating step configured to circulate water inside the tub to resupply the water to the tub, the circulating step implemented in a heating step.

Advantageous Effects of Invention

The present invention has following advantageous effects.

According to the control method of the present invention described above, it is possible to provide a control having a high efficiency washing cycle.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principle of the disclosure.

In the drawings:

FIG. 1 is a sectional view of an exemplary laundry machine as embodied and broadly described herein;

FIG. 2 is an exploded perspective view illustrating a laundry machine according to a second embodiment to which the spinning cycle control method is applied;

FIG. 3 is a sectional view illustrating a connecting state of FIG. 2;

FIG. 4 illustrate various drum motions and laundry movement patterns as embodied and broadly described herein;

FIG. 5 is a graph illustrating a water temperature and drive of a circulation pump in a washing cycle;

FIGS. 6 and 7 are graphs illustrating a rpm change of a drum in a spinning cycle;

FIG. 8 is a graph showing a relation of mass vs. a natural frequency.;

FIG. 9 is a graph illustrating vibration characteristics of the laundry machine.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows, a control method of a laundry machine according to the present invention will be described in reference to the accompanying drawings. Laundry machines according to various embodiments, to which control methods of the present invention can be applied, will be described in corresponding drawings first and the control methods will be described after that.

FIG. 1 is a diagram illustrating a laundry machine according to a first embodiment of the present invention, to which control methods according to various embodiments can be applied.

In reference to FIG. 1, a laundry machine 100 according to a first embodiment of the present invention includes a cabinet 10 configured to define an exterior appearance thereof, a tub 20 provided in the cabinet 10 to hold wash water therein and a rotatable drum 30 provided in the tub 20.

The cabinet 10 defines the exterior appearance of the laundry machine 100 and configuration elements, which will be described later, may be mounted in the cabinet 10. A door 11 is coupled to a front plate of the cabinet 10 and a user opens the door 11 to load laundry into the cabinet 10.

The tub 20 is provided in the cabinet 10 and it holds wash water therein. The drum 30 may be rotatable in the tub 20 and it accommodates laundry therein. In this case, a plurality of lifters 31 may be provided in the drum 30 and they lift and drop the laundry to implement washing.

The tub 20 is supported by a spring provided beyond the tub 20. A motor 40 is mounted to a rear surface of the tub 20 and the motor 40 rotates the drum 30. When vibration is generated by the drum rotated by the motor 40, the tub 20 provided in the laundry machine according to the first embodiment is vibrated in communication with the drum. In case the drum 30 is rotated, the vibration generated in the drum and the tub 20 may be absorbed by a damper 60 located under the tub 20.

As shown in FIG. 1, the tub 20 and the drum 30 may be provided in parallel to a base plate of the cabinet 10. Alternatively, although not shown in the drawings, rear portions of the tub 20 and the drum 30 may be oblique downward. This is because front portions of the tub 20 and the drum 30 had better be obliquely upward in case the user loads the laundry into the drum 30. A ball balancer 70 is provided in a front surface and/or a rear surface of the drum 30 to balance the vibration of the drum 30 in case the drum is rotated, especially, the drum is rotated at a high speed such as a dry-spinning cycle. The ball balancer will be described in detail later.

According to a laundry machine according to an embodiment, the tub may be fixedly supported to the cabinet or it may be supplied to the cabinet by a flexible supporting structure such as a suspension unit which will be described later. Also, the supporting of the tub may be between the supporting of the suspension unit and the completely fixed supporting.

That is, the tub may be flexibly supported by the suspension unit which will be described later or it may be complete-fixedly supported to be movable more rigidly. Although not shown in the drawings, the cabinet may not be provided unlike embodiments which will be described later. For example, in case of a built-in type laundry machine, a predetermined space in which the built-in type laundry machine will be installed may be formed by a wall structure and the like, instead of the cabinet. In other words, the built-in type laundry machine may not include a cabinet configured to define an exterior appearance thereof independently.

FIG. 2 is an exploded perspective view partially illustrating a laundry machine according to a second embodiment and FIG. 3 is a sectional view illustrating an assembled state of the laundry machine shown in FIG. 2.

In reference to FIGS. 2 and 3, the laundry machine according to this embodiment includes a tub 12 fixedly supported to a cabinet. The tub 12 may include a tub front 100 configured to define a front part thereof and a tub rear 120 configured to define a rear part thereof. The tub front 100 and the tub rear 120 are assembled to each other by screws and a predetermined space is formed in the assembled structure to accommodate the drum. The tub rear 120 may include an opening formed in a rear surface thereof and an inner circumference of the rear surface of the tub rear 120 is connected with an outer circumference of a rear gasket 250. An inner circumference of the rear gasket 250 is connected with a tub back 130. The tub back 130 includes a through-hole formed in a center thereof and a shaft passes the through-hole. The rear gasket 250 may be made of flexible material not to transmit the vibration of the tub back 130 to the tub rear 120.

The tub rear 120 includes a rear surface 128. The rear surface 128 of the tub rear 120, the tub back 130 and the rear gasket 250 define a rear wall of the tub. The rear gasket 250 is sealingly connected with the tub back 130 and the tub rear 120 and it prevents wash water held in the tub from leaking out. The tub back 130 is vibrated together with the drum during the rotation of the drum. Because of that, the tub back 130 is spaced apart a predetermined distance enough not to interfere with the tub rear 120. Since it is made of flexible material, the rear gasket 250 allows the tub back 130 to relative-move without interfering with the tub rear 120. The rear gasket 250 may include a corrugation part 252 extendible enough to allow such the relative movement of the tub back 130.

A foreign-substance-preventing member 200 is connected with a front portion of the tub front 100 to prevent foreign substances from coming between the tub and the drum. The foreign-substance-preventing member 200 is made of flexible material and it is fixedly installed to the tub front 100. The foreign-substance-preventing member 200 may be made of identical material to material used to make the rear gasket 250 and it will be referenced to as front gasket for convenience sake.

The drum 32 includes a drum front 300, a drum center 320 and a drum back 340. Ball balancers 310 and 330 are installed in front and rear portions of the drum, respectively. The drum back 340 is connected with a spider 350 and the spider 350 is connected with a shaft 351. The drum 32 is rotated in the tub by the rotational force transmitted via the shaft 351 from a motor.

The shaft 351 is directly connected with a motor 170, passing through the tub back 130. Specifically, the shaft 351 is directly connected with a rotor 174 composing the motor 170. A bearing housing 400 is coupled to a rear surface of the tub back 130 and the bearing housing 400 is located between the motor 170 and the tub back 130 to rotatably support the shaft 351.

A stator 172 is fixedly installed to the bearing housing 400 and the rotor 174 is located around the stator 172. As mentioned above, the rotor 174 is directly connected with the shaft 351. The motor 170 is an outer rotor type motor and it is directly connected with the shaft 351.

The bearing housing 400 is supported by a suspension unit with respect to a cabinet base 600 and the suspension unit 18 includes three perpendicular supporting suspensions and oblique-supporting suspensions configured to support the bearing housing obliquely in a forward and rearward direction.

The suspension unit 180 may include a first cylinder spring 520, a second cylinder spring 510, a third cylinder spring 500, a first cylinder damper 540 and a second cylinder damper 530.

The first cylinder spring 520 is provided between a first suspension bracket 450 and the cabinet base 600 and the second cylinder spring 510 is provided between a second suspension bracket 440 and the cabinet base 600.

The third cylinder spring 500 is directly connected between the bearing housing 400 and the cabinet base 600.

The first cylinder damper 540 is obliquely installed between the first suspension bracket 450 and a rear portion of the cabinet base. The second cylinder damper 530 is obliquely installed between the second suspension bracket 440 and the rear portion of the cabinet base.

The cylinder springs 520, 510 and 500 of the suspension unit 180 may be connected to the cabinet base 600 flexibly enough to allow the drum to move in a forward-and-rearward direction and a rightward-and-leftward direction, not completely fixed to the cabinet base. That is, the cylinder springs 520, 510 and 500 elastically support the drum to allow the drum to rotate vertically and horizontally with respect to the connected point with the cabinet base.

The perpendicular ones of the suspensions suspend the vibration of the drum elastically and the oblique ones dampen the vibration. That is, out of the vibration system configured of springs and damping means, the perpendicularly installed ones are employed as springs and the obliquely installed ones are employed as damping means.

The tub front 100 and the tub rear 120 are fixedly secured to the cabinet 110 and the vibration of the drum 32 is suspendingly supported by the suspension unit 180. Substantially, the structure of the tub 12 and the drum 32 may be separate. Even when the drum 32 is vibrated, the tub 12 may not be vibrated structurally.

The bearing housing 400 and the suspension brackets are connected by first and second weights 431 and 430.

A water supply line 722 is provided in the cabinet 110 and the water supply line 722 is connected with an external water supply source such as a water tap. The control part on-off-controls a water supply valve 720 to supply water to the tub 12 via the water supply line 722. An end of the water supply line 722 is connected with a front part of the tub 12 or the front gasket 200, to supply the water to the inside of the tub from the front part. In case a detergent box 710 is provided along the water supply line 722, the water may be supplied together with detergent.

In the meanwhile, a circulation pump 730 may be provided below the tub 12 and the circulation pump 730 circulates the water discharged from the tub 12 to re-supply it to the tub. In case the water is required to be circulated by the circulation pump 730 in the laundry machine according to the second embodiment, a vale 732 is adjusted and the circulation pump 730 is connected with a circulation line 744. An end of the circulation line is connected with the front part of the tub or the front gasket 200 to supply the water to the tub inside from the front part. In case the water is required to be drained from the tub 12, the circulation pump 730 is connected with a drainage line 742 to drain the water. Although not shown in the drawings, a circulation pump configured to circulate water and a drainage pump configured to drain the water may be provided separately. In this case, the circulation line and the drainage line are connected with the circulation pump and the drainage pump, respectively.

The tub 12 and the drum 32 may be installed in parallel to or oblique to the cabinet base 600 at a predetermined angle. In this case, rear portions of the tub 12 and the drum 32 may be oblique downward for the user to load the laundry into the drum 32 more smoothly.

If the laundry 1 is accommodated in the drum 30 and 32 and the drum 30 and 32 are rotated in the laundry machine according to the above embodiments, noise and vibration would be generated a lot according to the location of the laundry 1. For example, when the drum 30 and 32 is rotated with the laundry not distributed in the drum 30 and 32 uniformly (hereinafter, ‘eccentric rotation’, severe vibration and noise may occur. Especially, when the drum 30 and 32 is rotated at a high speed during the dry-spinning cycle, the vibration and the noise will be a problem

As a result, the laundry machine may include a ball balancer 70, 310 and 330 to prevent the vibration and noise generated by the eccentric rotation of the drum 30 and 32. The ball balancer 70, 310 and 330 may be provided in a front portion or rear portion or each of the front and rear portions.

The ball balancer 70, 310 and 330 is mounted to the rotatable drum 30 and 32 to reduce eccentricity. Because of that, the ball balancer 70, 310 and 330 may have a center of mass which is movable changeably. That is, the ball balancer (70, 310 and 330) may include a ball 72, 312 and 332 having a predetermined weight and a path in which the ball is movable along a circumferential direction.

Specifically, the ball is rotated by a friction force generated when the drum 30 and 32 is rotated. When the drum is rotated, the ball is not kept in the drum and it is rotated at a different speed from the drum. Here, the laundry generating the eccentricity is in close contact with an inner wall of the drum and it can be rotated at almost the same speed as the drum because of an enough friction force and the lift of the inner wall. As a result, the rotation speed of the laundry is different from that of the ball. The rotation speed of the laundry is faster than that of the ball in an initial rotation stage of the drum having a relatively slow speed. Precisely, an angular velocity of the laundry is faster than an angular velocity of the ball. Also, a phase difference between the ball and the laundry, that is, a phase difference with respect to a rotation center of the drum may changes continuously.

If the rotation speed of the drum is getting faster, the ball will be in close contact with an outer circumferential surface of the moving path because of a centrifugal force. At the same time, the ball is aligned at a position at which the phase difference between the ball and the laundry is approximately 90° to 180°. If the rotation speed of the drum is a predetermined value or more, the centrifugal force is getting larger enough the friction force between the circumferential surface and the ball to be a predetermined value or more, such that the ball may be rotated at the same speed as the drum. in this case, the ball is rotated at the same speed as the drum, with maintaining the position at which the phase difference with the laundry is 90° to 180°, preferably, approximately 180°. In this specification, the case of the ball being rotated at the predetermined position with respect to the drum will be referenced to as ‘eccentricity corresponding position’ or ‘ball-balanced’ for convenience sake.

As a result, when the load of the laundry is concentrated on a predetermined portion inside the drum 30 and 32, the ball provided in the ball balancer 70, 310 and 330 is moved to an eccentricity corresponding position to reduce the eccentricity.

In the meanwhile, the drum may be drivable in various ways in the above laundry machine. That is, a driving motion of the drum may be determined properly according to each of washing, rinsing and dry-spinning cycles, or the user may properly determine a driving motion of the drum according to characteristics of a selected course. As follows, various driving motions applicable to a control method according to the present invention will be described in detail.

FIG. 4 is a diagram illustrating various drum driving motions. FIG. 4 is a front view schematically illustrating the drum to shown the rotation of the drum. according to FIG. 4, the inside of the drum is divided into four parts in a counter-clockwise direction and the four parts are defined as first, second, third and fourth quadrants to explain the location of the laundry according to the rotation angle of the drum.

In reference to FIG. 4, the drum driving motions may be embodied by combination of the rotation direction, rotation speed and rotation angle of the drum. Also, the laundry located in the drum inside may have a different falling direction, falling point and shock when falling because of the drum driving motions. By extension, it may have different movement of the laundry inside the drum. The various drum driving motions may be embodied by controlling the motor configured to rotate the drum.

In the meanwhile, when the drum is rotated, the laundry is lifted by the lift (31, see FIGS. 1 and 132, see FIG. 3) provided in the inner circumferential surface of the drum. Because of that, the rotation speed, the rotation direction and the rotation angle of the drum are controlled and the shock applied to the laundry may be varied accordingly. That is, a mechanical force applied to the laundry such as the friction generated between laundry items, the friction generated between the laundry and the water and the dropping shock of the laundry may be varied and a degree of striking or scrubbing for the laundry may be varied accordingly. In addition, the rotation speed, rotation direction and rotation angle of the drum may be controlled and a degree of laundry distribution or turn-over inside the drum may be varied accordingly.

As a result, the control method of the laundry machine can provide various drum driving motions and the drum driving motions are varied according to each of the cycles and a specific step composing the cycle, such that an optimal mechanical force may be used to treat the laundry. Because of that, washing efficiency of the laundry may be improved and the time required by the optimal drum driving motion may be reduced.

In the meanwhile, the motor may be classified into a direct type connected with the shaft of the drum directly and an indirect type configured to transmit a rotation force to the drum via a pulley and the like. To embody the various drum driving motions, the motor 170 may be the direct type connected with the drum directly. In case of the rotation direction and torque of the motor, time delay or backlash may be prevented and the motion of the motor may be transmitted to the drum spontaneously in the direct type.

The drum driving motions are configured of a rolling motion, tumbling motion, step motion, swing motion, scrub motion and the like. As follows, each of the motions will be described in detail.

FIG. 4( a) is a diagram illustrating the rolling motion and each of FIG. 4 shows a rotation direction and rotation angle of the drum and the movement of the laundry inside the drum, to explain each of the motions.

In reference to FIG. 4( a), in the rolling motion, the motor 40 and 170 continuously rotates the drum 30 and 32 in a predetermined direction and the laundry located on the inner circumferential surface of the drum rotating along the rotation direction of the drum is dropped to the lowest point of the drum from the position at an angle of approximately less than 90°.

That is, once the motor 40 and 170 rotates the drum at approximately 35 RPM to 45 RPM, the laundry located in the lowest point of the drum 30 and 32 is lifted to a predetermined height along the rotation direction of the drum 30 and 32 and then it rolling-moves to the lowest point of the drum from the position of less than 90° with respect to the lowest point of the drum. In case the drum is rotated in a clockwise direction, the laundry is rolling in the third quadrant of the drum continuously. The laundry is washed by the friction with the water and the friction therewith and the friction with the inner circumferential surface of the drum in the rolling motion. The rolling motion enables the turn-over of the laundry implemented enough to generate an effect of soft scrubbing-like washing.

In the meanwhile, the drum RPM of the drum driving motion is determined by the relation with the centrifugal force, in case the drum is rotated. That is, the larger the drum RPM is, the larger centrifugal force is generated in the laundry inside the drum. If the centrifugal force is larger than the gravity, the laundry will be attached to the inner circumferential surface of the drum. If the centrifugal force is smaller than the gravity, the laundry may be dropped to the bottom surface of the drum. As a result, the movement of the laundry inside the drum may be varied by the relative size between the centrifugal force and the gravity. When the drum RPM is determined, the rotation force of the drum and the friction between the drum and the laundry may have to be put into consideration.

The drum RPM is determined for the centrifugal force to be smaller than the gravity in the above rolling motion. That is, the laundry is rolling-dropped along the rotation of the drum in the rolling motion and the centrifugal force has to be smaller than the gravity accordingly.

FIG. 4( b) is a diagram illustrating the tumbling motion.

In reference to FIG. 4( b), in the tumbling motion, the motor 40 and 170 continuously rotates the drum 30 and 32 in a predetermined direction and the laundry located on the inner circumferential surface of the drum is dropped to the lowest point of the drum from the position of approximately 90° to 110° with respect to the rotation direction of the drum.

In the tumbling motion, only if the drum is controlled to be rotated at a proper RPM in a predetermined direction, the mechanical force is generated between the laundry and the drum. Because of that, the tumbling motion is typically used in the washing and the rinsing.

That is, the laundry loaded into the drum 30 and 32 is located in the lowest point of the drum 30 and 32 before the motor 40 and 170 is driven. When the motor 40 and 170 provides a torque to the drum 30 and 32, the drum 30 and 32 is rotated and the lifter 132 provided in the inner circumferential surface of the drum lifts the laundry to a predetermined height from the lowest point of the drum. if the motor 40 and 170 rotates the drum 30 and 32 approximately at 46 RPM to 50 RPM, the laundry will be dropped to the lowest point of the drum from the position of approximately 90° to 110° with respect to the rotation direction of the drum. in the tumbling motion, the drum RPM is determined for a centrifugal force generated in the tumbling motion to be larger than the centrifugal force generated, in case the drum is rotated, and to be smaller than the gravity.

If the drum is rotated in the clockwise direction in the tumbling motion, the laundry is lifted to the second quadrant from the lowest point of the drum and then it is dropped to the lowest point of the drum. As a result, the tumbling motion enables the laundry to be washed by the shock generated by the friction with the water and the dropping shock. In the tumbling motion, a larger mechanical force larger than the mechanical force of the rolling motion may be used to implement washing and rinsing. Also, the tumbling motion is a motion in which the laundry is dropped inside the drum and it is effective in separating entangled laundry and distributing the laundry uniformly.

FIG. 4( c) is a diagram illustrating the step motion.

In reference to FIG. 4( c), in the step motion, the motor 40 and 70 rotates the drum 30 and 32 in a predetermined direction and the laundry located in the inner circumferential surface of the drum is controlled to be dropped to the lowest point of the drum from the highest point of approximately 180° with respect to the rotation direction of the drum.

Once the motor 40 and 170 rotates the drum 30 and 32 approximately at 60 RPM to 77 RPM or more, the laundry may be rotated by the centrifugal force until reaching the highest point of the drum, without being dropped. In the step motion, in case the laundry reaches near the highest point, the sudden brake is applied on the drum to maximize the shock applied to the laundry.

After rotating the drum 30 and 32 at a predetermined speed without dropping the laundry (approximately 60 RPM to 70 RPM or more) until the laundry reaches the highest point of the drum by using the centrifugal force, the motor 40 and 170 is controlled to supply a reverse torque to the drum 30 and 32 when the laundry is located near the highest point of the drum (180° with respect to the rotation direction of the drum). The laundry is lifted from the lowest point of the drum along the rotation direction of the drum. After that, when the drum is stopped momentarily by the reverse torque of the motor, the laundry is dropped from the highest point to the lowest point of the drum 30 and 32. As a result, the step motion enables the laundry to be washed by the shock generated while the laundry is dropped at the maximum height. A mechanical force generated in this step motion is larger than the mechanical force generated in the rolling motion or tumbling motion mentioned above.

In case the sudden brake is applied like in the step motion, the motor 40 and 170 may be reversing-phase-braked. The reversing-phase brake is a braking type of a motor by using a torque generated in a reverse direction with respect to a rotation direction of the motor. A phase of a current supplied to the motor may be reversed to generate a reverse torque and the reversing-phase brake enables the sudden brake to be applied to the motor. As a result, the reversing-phase brake is the most proper brake system to the step motion configured to apply the strong shock to the laundry.

According to FIG. 4( c), in the step motion, after moved to the highest point from the lowest point of the drum via the third and second quadrant sequentially in case the drum is rotated, the laundry is dropped to the lowest point out of the inner circumferential surface of the drum. As the dropping distance inside the drum is the largest in the step motion, a mechanical force may be applied to a small amount of the laundry.

Hence, the motor 40 and 170 re-applies a torque to the drum 30 and 32, the motor lifts the laundry located at the lowest point of the drum to the highest point along the same rotation direction. That is, when the laundry reaches the highest point after applying the torque to rotate the drum in the clockwise direction, the torque is applied to rotate the drum in the counter-clockwise direction and the drum is stopped suddenly. After that, a torque is applied to the drum to re-rotate in the clockwise direction and the step motion is embodied. As a result, the step motion is a motion used to wash the laundry by using the friction between the water drawn via the through hole (134, see FIG. 3) formed in the drum and the laundry and using the shock generated by the dropping the laundry when the laundry reaches the highest point of the drum.

FIG. 4( d) is a diagram illustrating the swing motion.

In reference to FIG. 4( d), in the swing motion, the motor 40 and 170 rotates the drum 30 and 32 in clockwise and counter-clockwise directions alternatively and the laundry is dropped at approximately the 90° to 130° position with respect to the rotation direction of the drum.

That is, once the motor 40 and 170 rotates the drum 30 and 32 at approximately 40 RPM in the counter-clockwise direction, the laundry located at the lowest point of the drum 30 and 32 is lifted a predetermined height in the counter-clockwise direction. after the laundry passes the 90° position with respect to the counter-clockwise direction of the drum, the motor stops the rotation of the drum for the laundry to be dropped to the lowest point of the drum from the 90° to 130° position with respect to the counter-clockwise direction of the drum.

Hence, the motor 40 and 170 rotates the drum 30 and 32 at approximately 40 RPM in the clockwise direction to lift the laundry a predetermined height in the clockwise direction along the rotation direction of the drum. After the laundry passes the 90° position with respect to the counter-clockwise direction of the drum, the motor stops the rotation of the drum and the laundry is dropped to the lowest point of the drum from the 90° to 130° position with respect to the clockwise direction of the drum.

That is, the swing motion is a motion in which the rotation and stop with respect to the predetermined direction and the rotation and stop with respect to the reverse direction may be repeated. The laundry lifted to a part of the second quadrant from the third quadrant of the drum is dropped softly and it is re-lifted a part of the first quadrant from the fourth quadrant of the drum to be dropped softly repeatedly. As a result, the laundry may be moved in a shape of a sided-‘8’ over the third and fourth quadrants of the drum in the swing motion.

At this time, the motor 40 and 170 may use rheostatic braking. According to the rheostatic braking, in case a current applied to a motor is off, the motor is employed as generator because of rotation inertia. In case the current applied to the motor is off, a direction of the current flowing in a coil of the motor will be changed into a reverse direction of the current before the power off and a force (Fleming's right hand rule) is applied along a direction which interferes with the rotation of the motor, to put the motor on the brake. Different from the reversing-phase braking, the rheostatic braking may not put the motor on the sudden brake but it may make the rotation direction of the drum changed softly. As a result, the swing motion adapts the rheostatic braking and the load put on the motor 40 and 170 may be reduced as much as possible. Moreover, mechanical abrasion of the motor 40 and 170 may be minimized and the shock applied to the laundry may be adjusted simultaneously.

FIG. 4( e) is a diagram illustrating the scrub motion,

In reference to FIG. (e), in the scrub motion, the motor 40 and 170 rotates the drum 30 and 32 in both of the clockwise and counter-clockwise directions alternatively and the reversing-phase braking is applied to the drum such that the laundry may be dropped from the 130° to 160° position with respect to the rotation direction of the drum.

That is, once the motor 40 and 170 rotates the drum 30 and 32 at approximately 60 RPM in the counter-clockwise direction, the laundry located in the lowest point of the drum 30 and 32 is lifted a predetermined height in the counter-clockwise direction. after the laundry passes an approximately 90° position with respect to the counter-clockwise direction of the drum, the motor provides the drum a reverse torque to stop the drum temporarily. If then, the laundry located on the inner circumferential surface of the drum will be dropped rapidly.

Hence, the motor 40 and 170 rotates the drum at approximately 60 RPM in the clockwise direction to lift the dropped laundry a predetermined height in the clockwise direction. after the laundry passes the 90° position with respect to the counter-clockwise direction of the drum, the motor 40 and 170 applies the reverse torque to the drum 30 and 32 and the rotation of the drum is stopped temporarily. As a result, the laundry located on the inner circumferential surface of the drum is dropped to the lowest point of the drum from the approximately 130° to 160° position with respect to the clockwise direction of the drum.

As a result, the laundry may be dropped rapidly from the predetermined height to be washed in the scrub motion. Here, the motor 40 and 170 may be reversing-phase-braked to stop the drum.

In the scrub motion, the rotation direction of the drum is changed rapidly and the laundry may not be out of the inner circumferential surface of the drum largely. Because of that, an effect of strong-scrubbing-like washing may be achieved in the scrub motion. In the scrub motion, it is repeated that the laundry moved to a part of the second quadrant via the third quadrant is dropped rapidly to be re-dropped after removed to a part of the first quadrant via the fourth quadrant. As a result, in the scrub motion, the lifted laundry is dropped along the inner circumferential surface of the drum repeatedly.

FIG. 4( f) is a diagram illustrating the filtration motion. In The filtration motion, the motor 40 and 170 rotates the drum 30 and 32 for the laundry not to be dropped from the inner circumferential surface of the drum and the water is sprayed into the drum.

That is, in the filtration motion, while the laundry after spread is rotated in close contact with the inner circumferential surface of the drum, the water is sprayed into the drum. The water is discharged out of the tub 120 from the laundry and the through hole 131 of the drum by the centrifugal force. Since the filtration motion widens a surface area of the laundry and it enables the water to pass through the laundry, the wash water may be enabled to pass through the laundry and the wash water may be supplied to the laundry uniformly.

FIG. 4( g) is a diagram illustrating the squeeze motion. In the squeeze motion, the motor 40 and 170 rotates the drum 30 and 32 for the laundry not to be dropped from the inner circumferential surface of the drum by the centrifugal force and after that, the motor lowers the rotation speed of the drum 30 and 32 to separate the laundry from the inner circumferential surface of the drum. This process is repeated and the water is sprayed into the drum during the rotation of the drum.

That is, the drum is rotated at the speed enough not to drop the laundry from the inner circumferential surface of the drum continuously in the filtration motion. In contrast, the rotation speed of the drum is changed to repeat the process of closely contacting the laundry in and separating the laundry from the inner circumferential surface.

The process of the water spraying into the drum 30 and 32 in the filtration motion and the squeeze motion may be implemented by using a circulation path and a pump although not shown in FIG. 1. The pump is in communication with the lower surface of the tub 120 and it presses the wash water. An end of the circulation path is connected with the pump and the water is sprayed from the upper portion of the drum into the drum via the other end of the circulation path.

The circulation path and the pump mentioned above are required elements in case of spraying the water held in the tub and the present invention may not exclude a case of spraying the water via a path connected with an external water supply source located outside of the cabinet.

In the meanwhile, FIG. 5 is a diagram illustrating the step motion more specifically. Once the motor 40 and 170 applies the torque to the drum 30 and 32 in the predetermined direction, the drum is rotated in the predetermined direction and the laundry is lifted in the state of the close contact with the inner circumferential surface of the drum. At this time, the drum may be rotated at approximately 60 RPm or more to lift the laundry in close contact with the inner circumferential surface of the drum. Here, the rotation speed of the drum is determined by the relation with an inner diameter of the drum and the determined rotation speed may have the centrifugal force larger than the gravity.

Just before the laundry reaches the highest point of the drum, passing the 90° position with respect of the rotation direction of the drum 30 and 32, the motor 40 and 170 is reversing-phase-braked to stop the rotation of the drum temporarily. The timing point of the reversing-phase-braking with respect to the motor 40 and 170 is closely related to the location of the laundry inside the drum. Because of that, a device used to determine or expect the location of the laundry may be provided and a sensing device including a Hall Effect sensor configured to determine a rotation angle of a rotor may be one of examples.

The control part may determine a rotation direction as well as the rotation angle of the rotor by using the hall sensor. This technical feature is well-known knowledge to anyone skilled in the art and detailed description thereof will be omitted accordingly.

The control part may determine the rotation angle of the drum by using the sensing device and it controls the motor 40 and 170 to be reversing-phase-braked before the drum has a rotation angle of 180°. Here, the reversing-phase-braking means that a reverse current is applied to rotate the drum in a reverse direction. For example, after a current is applied to the motor to rotate the drum in a clockwise direction, a reverse current is rapidly applied to rotate the drum in a clockwise direction.

As a result, the drum rotated in the clockwise direction is stopped in a moment and the rotation angle at this time is substantially 180° to drop the laundry to the lowest point from the highest point of the drum. After that, the current is continuously applied to rotate the drum in the clockwise direction.

FIG. 5 shows that the drum is rotated in the clockwise direction. Here, while the drum is rotated in the counter-clockwise direction, the step motion may be implemented. Here, the step motion generates a lot of load to the motor 40 and 170 and a net acting ratio of the step motion may be reduced.

The net acting ratio is a ratio of a motor driving time to a totaled value of the driving time and the stopping time of the motor 40 and 170. If the net acting ratio is ‘1’ it means that the motor is driven without a stopping time. The step motion may be implemented at approximately 70% of the net acting ratio, considering the load of the motor. For example, the motor may be stopped for 4 seconds after driving for 10 seconds.

FIG. 6 is a diagram illustrating the scrub motion more specifically. Once the motor 40 and 170 applies the torque to the drum 30 and 32, the laundry inside the drum is rotated in the clockwise direction. Here, the motor 40 and 170 may be controlled to rotate the drum 30 and 32 at approximately 60 RPM or more to rotate the laundry in close contact with the inner circumferential surface of the drum. After that, when the laundry passes the 90° position with respect to the rotation direction of the drum, the motor 40 and 170 is reversed-phase-braked and the laundry in close contact with the inner circumferential surface of the drum is dropped to the lowest point of the drum accordingly.

When the laundry is dropped to the lowest point, the motor 40 and 170 applies the torque to the drum to rotate the drum in the counter-clockwise direction. As a result, the laundry is rotated in the counter-clockwise direction, in close contact with the inner circumferential surface of the drum. When the laundry is located between the 90° position with respect to the counter-clockwise direction and the highest point of the drum from the lowest point, the motor is reversing-phase-braked and the laundry in close contact with the inner circumferential surface of the drum is dropped to the lowest point of the drum.

The scrub motion described above generates a lot of load applied to the motor 40 and 170, like the step motion. As a result, a net acting ratio of the scrub motion may be reduced. For example, the scrub motion is implemented for 10 seconds and after that, it is stopped for 4 seconds and this process is repeated for the net acting ratio to be 70%.

Although not shown in the drawings, the braking type of the motor in the scrub motion is changed into the rheostatic braking in the swing motion. The timing point of the rheostatic braking is changed into the moment when the laundry reaches the 90° position with respect to the rotation direction of the drum, and the detailed description of the swing motion will be omitted accordingly.

FIG. 7 is a graph illustrating comparison of washing ability and a vibration level of each motion shown in FIG. 4. A horizontal axis presents the washing ability and it is easier to separate contaminants contained in the laundry as moving to the left. A vertical axis presents the vibration or noise level and the vibration level is higher as moving upward, with the washing time for the same laundry being reduced.

The step motion and the scrub motion are proper to washing courses implemented to reduce the washing time when the laundry has severe contaminant. The step motion and the scrub motion have a high vibration/noise level and they are not proper to washing courses implemented to wash sensitive fabric and to minimize noise and vibration.

The rolling motion has a good washing ability and a low vibration level, with minimized laundry damage and low motor load. As a result, the rolling motion may be proper to all of the washing courses, especially, to detergent dissolution in an initial washing stage and to wet the laundry.

The tumbling motion has a lower washing ability than the scrub motion and a middle vibration level in comparison to the scrub motion and the rolling motion. The rolling motion has the lower vibration level but it has a longer washing time than the tumbling motion. Because of that, the tumbling motion may be applicable to all of the washing courses and it is proper to a washing course required to distribute the laundry uniformly.

The squeeze motion has a similar washing ability to the tumbling motion and a higher vibration level than the tumbling motion. The squeeze motion repeats the process of closely contacting the laundry in and separating the laundry from the inner circumferential surface of the drum and in this process, the wash water is discharged outside of the drum after passing the laundry. As a result, the squeeze motion is proper to the rinsing.

The filtration motion has a lower washing ability than the squeeze motion and a similar noise level to the rolling motion. In the filtration motion, the water passes the laundry and discharged out of the drum, with the laundry in close contact with the inner circumferential surface of the drum. As a result, the filtration motion is proper to a course which requires wetting of the laundry.

The swing motion has the lowest vibration level and washing ability and it is proper to a low noise and low vibration washing course and to a course for washing sensitive clothes.

As mentioned above, each drum driving motion has advantages and disadvantages and it is preferable that those various drum driving motions are used properly. Each drum driving motion may have advantages and disadvantages in the relation with the laundry amount. Even in case of the same course and cycle, the various drum driving motions may be used properly with respect to the relation with the laundry amount.

As follows, a control method of the laundry machine including the drum driving motions described above will be described. The laundry machine typically includes washing, rinsing and dry-spinning cycles and those cycles will be described from now on. Here, the washing cycle is a part of various courses or it may be implemented independently.

The washing cycle may include a water supplying step configured to supply water and detergent to the tub 12 and 20 or the drum 30 and 32 to dissolve the detergent in the water. That is, the water and the detergent are mixedly supplied to wash the laundry. In addition, the washing cycle may include a main-washing step configured to drive the drum to wash the laundry. Here, the water supplying step may be a preparing step for the main washing step. As a result, it is preferable to improve efficiency of the water supplying step to improve efficiency of the washing cycle (including washing efficiency and time-reducing efficiency).

The washing cycle may include a laundry wetting step and/or heating step implemented between the water supplying step and the main washing step. The control method which will be described is relating to the water supplying step of the washing cycle and it will be described in detail.

The control part supplies wash water to the tub 12 and 20 in the water supplying step. Specifically, the control part opens the water supply valve 720 and supplies the water to the tub 12, with the water passing the water supply line 722 and the detergent box 710.

Since the detergent is supplied together with the water in the water supplying step, detergent dissolution may be completely implemented during the water supply step to improve the efficiency of the washing cycle. As a result, in the water supplying step, a predetermined process may be implemented to accelerate the detergent dissolution in the water. If the water contacts with the laundry partially during the water supplying, the water fails to wet the laundry uniformly and the efficiency of the washing cycle may deteriorate. Although the laundry wetting step is provided in the washing cycle, the water supplying step may include a process of making the laundry wet uniformly by the water. As follows, various embodiments of the detergent dissolution accelerating process and the uniformly wetting laundry process will be described.

First of all, to accelerate the detergent dissolution, a motion (drum driving motion) of moving the laundry inside the drum may apply a strong mechanical force to the water and the laundry. As a result, the step motion is preferable in the water supplying step to accelerate the detergent dissolution, because the laundry lifted along the rotating drum is dropped out of the inner circumferential surface of the drum by the braking of the drum and because this is repeated in the step motion. Of course, the scrub motion in which the laundry lifted along the rotating drum is repeatedly dropped and lifted by the braking and reverse-rotating of the drum may be implemented in the water supplying step. In the step motion and the scrub motion, the drum after rotated is stopped rapidly and the moving direction of the laundry is changed rapidly. As a result, they may be motions capable of applying a strong shock to the laundry and the water, such that the strong mechanical force may be provided in an initial stage of the water supplying step and that the detergent dissolution may be accelerated, only to improve the efficiency of the washing cycle.

The detergent dissolution may be accelerated by repeating the sequential combination of the step and scrub motions. In this case, different types of drum driving motions are combined and the laundry movement type and the water flow type may be diversified. As a result, the efficiency of the washing cycle may be improved more.

As mentioned above, the water supplying step is a preparing step of the main washing step. Because of that, the detergent dissolution and the laundry wetting have to be implemented quickly and completely in the water supplying step and they may be implemented regardless of the amount of the laundry. However, considering the limited capacity of the drum, the limited water able to be supplied to the drum, the drum driving motion of the water supplying step may be controlled differently according to the laundry amount. This is because the drum driving motion capable of achieving the maximum effect of the detergent dissolution and laundry wetting may be differentiated according to the laundry amount.

A laundry amount determining step configured to determine the amount of the laundry accommodated in the drum may be implemented before the water supplying step. The drum driving motion in the water supplying step may be controlled differently according to the result of the laundry amount determining step.

Such the laundry amount determining may be implemented by measuring the current required to rotate the drum. For example, the currents required to implement the tumble motion may be measured. In case the drum is rotated, the current value applied by the control part to implement the tumble motion may be differentiated according to the laundry amount and the laundry amount may be determined.

If the laundry amount determined in the laundry amount determining step is a preset laundry amount level or more, the process for the detergent dissolution may be controlled not to be implemented. That is, the process configured to accelerate the detergent dissolution may be controlled to be implemented, if the laundry amount is the preset level of less. This is because the drum driving motion capable of supplying the strong mechanical force is more effective in case the laundry amount is small and because the small amount of the laundry can be wet by the water sufficiently. That is, the small amount of the laundry means that a surface area of the laundry required to contact with the water is small and that the detergent dissolution and laundry wetting can be implemented by the mechanical force used to turn over the laundry in a short time. As a result, the effect of the main washing may be achieved partially by the step motion or scrub motion and an effect of the reduced time required to implement the main washing may be expected.

In contrast, in case of the large amount of the laundry, the mechanical force may not be enough and the laundry may not contact with the water enough. When the laundry is crumbled, the water fails to be supplied to items inside the crumble laundry enough.

As a result, if the laundry amount is a preset level or more, the process of detergent dissolution acceleration is omitted and the laundry wetting step may start. When the laundry amount is a preset level or more, it is more preferable to accelerate the detergent dissolution that the laundry contacts with the water enough. For that, a circulating step configured to circulating the water held in the tub to re-supply it to the drum may be implemented in the water supplying step.

According to the laundry machine according to the second embodiment described above, the tub 12 is directly fixed to the cabinet 110 and the drum 32 is provided in the tub 12. Since only the drum 32 is rotated in the laundry machine according to the second embodiment, with the tub 12 fixedly installed, it is important to prevent the contact between the drum 32 and the tub 12 during the rotation of the drum. As a result, the distance between the tub 12 and the drum may be formed larger in the laundry machine than in the conventional laundry machine.

If the distance between the tub 12 and the drum 32 is widened, the laundry inside the drum 32 may not be wet enough during the water supply to the tub. To enable the laundry to be wet enough when the water is supplied, the laundry machine according to the second embodiment operates the circulation pump 730 and water held in the tub may be circulated. For example, the circulation pump 730 may be driven continuously or at a predetermined interval, with the water supply valve being open.

According to the laundry machine of the second embodiment, the drum 32 is connected with the tub back 30. The tub back 130 is supported by the suspension unit 180 via the bearing housing 400, not by the tub 12. as a result, compared with the drum 30 supported by the tub back 130 directly connected with the tub 12 in the laundry machine according to the first embodiment, the drum 32 provided in the laundry machine according to the second embodiment, especially, the front part of the drum 32 has a large degree of freedom.

In case the water is supplied to the tub 12, the water supply line 722 and the circulation line 744 supply the water in the front portion of the tub 12 and the laundry located in the front portion of the drum may be wet first. Because of that, the load applied to the front portion of the drum 32 is larger than the load applied to the rear portion and the front portion of the drum 32 may go downward. If the front portion of the drum goes downward, the noise and vibration generated during the rotation of the drum would be increased and rather than that, it would contact with an inner surface of the tub 12. Because of that, it is required during the water supply in the laundry machine according to the second embodiment to wet the laundry located in both of the front and rear portions of the drum 32 uniformly.

As follows, a control method of wetting the laundry located in both of the front and rear portions of the drum uniformly according to embodiments of the present invention will be described, when the water supply is implemented in the laundry machine according to the second embodiment of the present invention.

In case the water is supplied in the water supplying step according to the control method of the first embodiment, the circulation pump 730 is driven to circulate the water and the drum 32 is driven simultaneously. When the drum 32 is driven, the control part controls the drum 32 to be driven according to the scrub motion of the drum driving motions described above.

The distance between the drum 32 and the tub 12 in the laundry machine according to the second embodiment is larger than the distance between them in the conventional laundry machine. Because of that, when the tumbling motion is applied to the drum 32 during the water supply like in the conventional laundry machine, the laundry located in the rear portion of the drum fails to be wet enough. That is, as the gap between the drum 32 and the tub 12 is larger than the gap formed in the conventional laundry machine, the water located between the drum and the tub will not be lifted by the rotation of the drum, not to wet the laundry located in the rear portion of the drum.

As a result, when the water supplying step is implemented according to this control method, the scrub motion is implemented instead of the tumbling motion. As mentioned above, the scrub motion rotates the drum at the higher RPM than the tumbling motion and the water located between the drum 32 and the tub 12 is lifted by the rotation of the drum 32, to fall onto the laundry.

Especially, the rear portions of the drum 32 and the tub 12 are obliquely structured in the laundry machine according to the second embodiment. Because of that, the scrub motion enables the water located in the rear portion of the tub 12 to be supplied to the top of the laundry smoothly. Also, the scrub motion rapidly changes the rotation direction of the drum 32 in the clockwise direction and counter-clockwise direction. Because of that, vortex is generated in the wash water by the rapid reversing of the rotation applied to the drum such that the laundry located in the front and rear portions of the drum may be wet uniformly.

When the water supply valve 720 is opened for the water supply, the drum 32 is driven and rotated and the laundry is moved inside the drum 32 according to the driving of the drum 32. in this case, the water supplied via the water supply line 722 connected with the front part of the tub 12 may be supplied to the moving laundry located in the front portion of the drum 32 mostly and the laundry located in the front portion is wet faster than the laundry located in the rear portion of the drum 32.

Until a predetermined time passes after the water supply valve 720 to supply the water or the water reaches a predetermined water level, the control method according to the second embodiment may not drive the drum 32. If the drum 32 is not driven for the predetermined time or until the water reaches the predetermined water level, the water supplied via the water supply line 722 may be collected in the lower portion of the tub 12 mostly. Here, the predetermined water level may be determined in consideration of the distance between the tub 12 and the drum. The predetermined time may be determined according to the capacities of the tub 12 and the drum 32 and the amount of the laundry.

Especially, the rear portion of the tub 12 in the laundry machine mentioned above is installed obliquely downward and a lot of the water is collected in the rear portion of the tub 12. When the drum 32 is rotated in a predetermined time, the laundry located in the rear portion of the drum 32 may be wet by the water collected in the rear portion of the tub 12. When the drum 32 is driven according to the control method of the second embodiment, the drum driving motion may be embodied as the tumbling motion or scrub motion.

In case the water supply valve 720 is open to supply the water according to the second embodiment of the control method, without driving the drum 32, the water supply valve 720 may be on-off-controlled. That is, when the water supply valve 720 is opened for the water supply, the water may have a predetermined pressure because of the water pressure of the external water supply source such as a water tap. In this case, the water supplied via the water supply line 722 may be supplied to the front portion of the drum by the water pressure, to wet the laundry located in the front portion of the drum.

As a result, when the water supply is implemented in the control method according to the second embodiment, the water supply valve 720 may be on and off repeatedly, not opened continuously. The water supply valve 720 may be controlled to be on and off for the supplied water to have a predetermined water pressure not to flow into the drum 32 directly. Here, the water pressure not to flow the water into the drum directly may mean a water pressure enabling the water supplied via the water supply line 722 to fall down along the drum, tub or door and to be collected in the lower portion of the tub 12, not to be sprayed into the drum by the water pressure. The water having fallen along the drum, tub or door may be collected in the rear portion of the tub 12 and the description after that is similar to the description mentioned above. The repeated description will be omitted accordingly.

In the meanwhile, when the water is supplied in the water supplying step, the laundry may be crumbled into a lump and a partial amount of the laundry may be wet. Especially, the laundry located in a center of the crumbled lump may not be wet and only the laundry located in the outer portion of the crumbled lump. If only the part of the laundry is wet, washing will not be implemented smoothly in the washing cycle, only to deteriorate washing efficiency. In case the laundry is crumbled into a lump, a control method according to a third embodiment configured to wet the crumbled laundry uniformly will be described.

The control part opens the water supply valve 720 for the water supply and it drives the circulation pump 730 to circulate the water simultaneously. The control part may drive the drum 32 in the filtration motion.

That is, the control part may control the drum to be rotated at a predetermined RPM. Here, the predetermined RPM is determined to be a RPM enabling the laundry to be in close contact with the inner wall of the drum, not dropped by the gravity when the drum is rotated. As a result, the predetermined RPM may be set for a centrifugal force applied to the rotating drum to be larger than an acceleration of gravity and the predetermined RPM may be set lower than an excessive period of the laundry machine in which resonance is generated (approximately 200 RPM to 35 RPM) if the drum is rotated at the RPM higher than the excessive period, noise and vibration generated by the resonance might be remarkably increased. As a result, the predetermined RPM may be set at approximately 100 RPM to 170 RPM.

Once the control part rotates the drum 32 at the predetermined RPM, the laundry is in close contact with the inner wall of the drum 32 because of the centrifugal force and the water supplied via the circulation line 744 and the water supply line 722 is distributed according to the rotation of the drum 32. The distributed water is supplied to the drum 32 toward the laundry stuck to the inner wall of the drum 32, such that the laundry may be wet uniformly.

In the meanwhile, the control methods configured to wet the laundry uniformly are described, applied to the laundry machine according to the second embodiment, and the present invention is not limited thereto. For example, the control methods may be applicable to the laundry machine according to the first embodiment.

One of the process of the detergent dissolution acceleration and the process of wetting the laundry uniformly described above or both of them may be implemented in the water supplying step. Both of the two processes may be implemented sequentially or repeatedly as well as sequentially or reversely, and various combinations of the two processes may be possible.

Hence, the control part controls the drum to be rotated in the laundry wetting step to wet the laundry. In case the water does not have to be heated, a heating step configured to heat the water by using the heater provided in the tub may be implemented. After that, the control part implements the main washing step by driving the drum 32 and the circulation pump 730 simultaneously. The drum driving motion in the main washing step may be selectable out of the drum driving motions according to the course selected by the user. The circulation pump 730 is driven at a predetermined interval and the water held in the tub 12 is circulated.

In the meanwhile, a drum inside of the drum type washing machine is visible from outside via the door 11. The various drum driving motions may be implemented in the washing cycle according to the embodiment and the washing course including the washing cycle. As a result, the user may see the various drum driving motions implemented in the drum inside directly. That is, a soft striking type of washing (tumbling motion), a strong striking type of washing (step motion), soft scrubbing type of washing (rolling motion) and a strong scrubbing type of washing (scrub motion) may be visibly identified. Because of that, the user can sense that the washing is implemented well and this may create an effect of improved user sensibility satisfaction as well as the effect of the substantially improved washing efficiency.

Meanwhile, FIG. 8 illustrates a graph showing a relation of mass vs. a natural frequency. It is assumed that, in vibration systems of two laundry machines, the two laundry machines have mass of m0 and m1 respectively and maximum holding laundry amounts are Δm, respectively. Then, the transition regions of the two laundry machines can be determined taking Δnf0 and Δnf1 into account, respectively. In this instance, amounts of water contained in the laundry will not be taken into account, for the time being.

In the meantime, referring to FIG. 8, the laundry machine with smaller mass m1 has a range of the transition region greater than the laundry machine with greater mass m0. That is, the range of the transition region having variation of the laundry amount taken into account becomes the greater as the mass of the vibration system becomes the smaller.

The ranges of the transition regions will be reviewed on the related art laundry machine and the laundry machine of the embodiment.

The related art laundry machine has a structure in which vibration is transmitted from the drum to the tub as it is, causing the tub to vibrate. Therefore, in taking the vibration of the related art laundry machine into account, the tub is indispensible. However, in general, the tub has, not only a weight of its own, but also substantial weights at a front, a rear or a circumferential surface thereof for balancing. Accordingly, the related art laundry machine has great mass of the vibration system.

Opposite to this, in the laundry machine of the embodiment, since the tub, not only has no weight, but also is separated from the drum in view of a supporting structure, the tub may not be put into account in consideration of the vibration of the drum. Therefore, the laundry machine of the embodiment may have relatively small mass of the vibration system.

Then, referring to FIG. 8, the related art laundry machine has mass m0 and the laundry machine of the embodiment has mass m1, leading the laundry machine of the embodiment to have a greater transition region, at the end.

Moreover, if the amounts of water contained in the laundry are taken into account simply, ?m in FIG. 8 will become greater, making a range difference of the transition regions even greater. And, since, in the related art laundry machine, the water drops into the tub from the drum even if the water escapes from the laundry as the drum rotates, an amount of water mass reduction come from the spinning is small. Since the laundry machine of the embodiment has the tub and the drum separated from each other in view of vibration, the water escaped from the drum influences the vibration of the drum, instantly. That is, the influence of a mass change of the water in the laundry is greater in the laundry machine of the embodiment than the related art laundry machine.

Under above reason, though the related art laundry machine has the transition region of about 200˜270 rpm, A start RPM of the transient region of the laundry machine according to this embodiment may be similar to a start RPM of the transient region of the conventional laundry machine. An end RPM of the transient region of the laundry machine according to this embodiment may increase more than a RPM calculated by adding a value of approximately 30% of the start RPM to the start RPM. For example, the transient region finishes at an RPM calculated by adding a value of approximately 80% of the start RPM to the start RPM. According to this embodiment, the transient region may include a RPM band of approximately 200 to 350 rpm.

In the meantime, by reducing intensity of the vibration of the drum, unbalance may be reduced. For this, even laundry spreading is performed for spreading the laundry in the drum as far as possible before the rotation speed of the drum enters into the transition region.

In a case, a balancer is used, a method may be put into account, in which the rotation speed of the drum passes through the transition region while movable bodies provided in the balancer are positioned on an opposite side of an unbalance of the laundry. In this instance, it is preferable that the movable bodies are positioned at exact opposite of the unbalance in middle of the transition region.

However, as described above, the transient region of the laundry machine according to this embodiment is relatively wide in comparison to that of the conventional laundry machine. Because of that, even if the laundry even-spreading step or ball balancing is implemented in a RPM band lower than the transient region, the laundry might be in disorder or balancing might be failed with the drum speed passing the transient region.

As a result, balancing may be implemented at least one time in the laundry machine according to this embodiment before and while the drum speed passing the transient region. Here, the balancing may be defined as rotation of the drum at a constant-speed for a predetermined time period. Such the balancing allows the movable body of the balancer to the opposite positions of the laundry, only to reduce the unbalance amount. By extension, the effect of the laundry even-spreading. Eventually, the balancing is implemented while the drum speed passing the transient region and the noise and vibration generated by the expansion of the transient region may be prevented.

Here, when the balancing is implemented before the drum speed passing the transient region, the balancing may be implemented in a different RPM band from the RPM of the conventional laundry machine. For example, if the transient region starts at 200 RPM, the balancing is implemented in the RPM band lower than approximately 150 RPM. Since the conventional laundry machine has a relatively less wide transient region, it is not so difficult for the drum speed to pass the transient region even with the balancing implemented at the RPM lower than approximately 150 RPM. However, the laundry machine according to this embodiment has the relatively wide expanded transient region as described above. if the balancing is implemented at the such the low RPM like in the conventional laundry machine, the positions of the movable bodies might be in disorder by the balancing implemented with the drum speed passing the transient region. Because of that, the laundry machine according to this embodiment may increase the balancing RPM in comparison to the conventional balancing RPM, when the balancing is implemented before the drum speed enters the transient region. That is, if the start RPM of the transient region is determined, the balancing is implemented in a RPM band higher than a RPM calculated by subtracting a value of approximately 25% of the start RPM from the start RPM. For example, the start RPM of the transient region is approximately 200 RPM, the balancing may be implemented in a RPM band higher than 150 RPm lower than 200 RPM.

Moreover, the unbalance amount may be measured during the balancing. That is, the control method may further include a step to measure the unbalance amount during the balancing and to compare the measured unbalance amount with an allowable unbalance amount allowing the acceleration of the drum speed. If the measured unbalance amount is less than the allowable unbalance amount, the drum speed is accelerated after the balancing to be out of the transient region. In contrast, if the measured unbalance amount is the allowable unbalance amount or more, the laundry even-spreading step may be re-implemented. in this case, the allowable unbalance amount may be different from an allowable unbalance amount allowing the initial accelerating.

In addition, vibration characteristics of the laundry machine according to the embodiment of the present invention will now be described with reference to FIG. 9.

As the rotation speed of the drum is increased, a region (hereinafter, referred to as transient vibration region) where irregular transient vibration with high amplitude occurs is generated. The transient vibration region irregularly occurs with high amplitude before vibration is transited to a steady-state vibration region (hereinafter, referred to as “steady-state region”), and has vibration characteristics determined if a vibration system (laundry machine) is designed. Though the transient vibration region is different according to the type of the laundry machine, transient vibration occurs approximately in the range of 200 rpm to 270 rpm. It is regarded that transient vibration is caused by resonance. Accordingly, it is necessary to design the balancer by considering effective balancing at the transient vibration region.

In the mean time, as described above, in the laundry machine according to the embodiment of the present invention, the vibration source, i.e., the motor and the drum connected with the motor are connected with the tub 12 through the rear gasket 250. Accordingly, vibration occurring in the drum is little forwarded to the tub, and the drum is supported by a damping means and the suspension unit 180 via a bearing housing 400. As a result, the tub 12 can directly be fixed to a cabinet 110 without any damping means.

As a result of studies of the inventor of the present invention, vibration characteristics not observed generally have been found in the laundry machine according to the present invention. According to the general laundry machine, vibration (displacement) becomes steady after passing through the transient vibration region. However, in the laundry machine according to the embodiment of the present invention, a region (hereinafter, referred to as “irregular vibration”) where vibration becomes steady after passing through the transient vibration region and again becomes great may be generated. For example, if the maximum drum displacement or more generated in an RPM band lower than the transient region or the maximum drum displacement or more of steady state step in a RPM band higher than the transient region is generated, it is determined that irregular vibration is generated. Alternatively, if an average drum displacement in the transient region, +20% to −20% of the average drum displacement in the transient region or ⅓ or more of the maximum drum displacement in the natural frequency of the transient region are generated, it may be determined that the irregular vibration is generated.

However, as a result of the studies, irregular vibration has occurred in a RPM band higher than the transient region, for example has occurred at a region (hereinafter, referred to as “irregular vibration region”) in the range of 350 rpm to 1000 rpm, approximately. Irregular vibration may be generated due to use of the balancer, the damping system, and the rear gasket. Accordingly, in this laundry machine, it is necessary to design the balancer by considering the irregular vibration region as well as the transient vibration region.

For example, the balancer is provide with a ball balancer, it is preferable that the structure of the balancer, i.e., the size of the ball, the number of balls, a shape of the race, viscosity of oil, and a filling level of oil are selected by considering the irregular vibration region as well as the transient vibration region. When considering the transient vibration region and/or the irregular vibration region, especially considering the irregular vibration region, the ball balancer has a greater diameter of 255.8 mm and a smaller diameter of 249.2. A space of the race, in which the ball is contained, has a sectional area of 411.93 mm2. The number of balls is 14 at the front and the rear, respectively, and the ball has a size of 19.05 mm. Silicon based oil such as Poly Dimethylsiloxane (PDMS) is used as the oil. Preferably, oil has viscosity of 300CS at a room temperature, and has a filling level of 350 cc.

In addition to the structure of the balancer, in view of control, it is preferable that the irregular vibration region as well as the transient vibration region is considered. For example, to prevent the irregular vibration, if the irregular vibration region is determined, the balancing may be implemented at least one time before, while and after the drum speed passes the irregular vibration region. Here, if the rotation speed of the drum is relatively high, the balancing of the balancer may not be implemented properly and the balancing may be implemented with decreasing the rotation speed of the drum. however, if the rotation speed of the drum is decreased to be lower than the transient region to implement the balancing, it has to pass the transient region again. In decreasing the rotation speed of the drum to implement the balancing, the decreased rotation speed may be higher than the transient region.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A control method of a laundry machine comprising: a circulating step configured to circulate water inside the tub to resupply the water to the tub, the circulating step implemented in a heating step.
 2. The control method as claimed in claim 1, wherein the circulating step implemented in the heating step has a relatively short operation time than circulating steps implemented in a water supplying step and a laundry wetting step have.
 3. The control method as claimed in claim 1, wherein the heating step drives the drum in one of a tumbling motion, a rolling motion and a swing motion.
 4. The control method as claimed in claim 3, wherein the circulating step and the driving of the drum are stopped and water is re-supplied to a predetermined water level, when a water level of the tub is decreased less than a reference level.
 5. The control method as claimed in claim 4, wherein driving of a heater is stopped when the water is re-supplied to the tub.
 6. The control method of claim 4, wherein the reference water level is determined to be higher a predetermined distance than the height of the heater.
 7. The control method as claimed in claim 4, wherein the heating step is re-implemented after the re-supply of the water to the tub.
 8. The control method as claimed in claim 1, wherein the laundry machine comprises a driving unit comprising a shaft connected to a drum, a bearing housing to rotatably support the shaft, and a motor to rotate the shaft, and a suspension assembly is connected to the driving unit.
 9. The control method as claimed in claim 1, wherein the laundry machine comprises a rear gasket for sealing to prevent washing water from leaking from a space between a driving unit and a tub, and enabling the driving unit movable relative to the tub.
 10. The control method as claimed in claim 1, wherein a tub is supported rigidly more than a drum being supported by a suspension assembly. 